Communication Service Providers are deploying a large number of Ethernet and IP services across networks and across a large number of Network Equipment Manufacturers (NEMs).
The support for Ethernet test and turn-up functions such as latching loopback (LLB) functions differs largely from one network equipment provider to another and this dramatically increases the operational complexity of deploying Ethernet based services across networks and across equipment vendors.
Network Elements (NEs) in today's networks are owned and managed by many parties that have interests in different portions of the Ethernet networks. To support the different needs of these parties, different types of services are being deployed over these networks.
One type of service being deployed is Ethernet Virtual Connections (EVCs). EVCs are logical representations of Ethernet services as defined by associations between 2 or more physical interfaces. An EVC represents a logical relationship between Ethernet user-to-network interfaces (UNI) in a provider-based Ethernet service. EVCs may be deployed to differentiate traffic on Ethernet networks.
When a telecommunications service provider offers a Metro Ethernet service that is compliant with the Metro Ethernet Forum (MEF) specifications, the service has two basic elements: the UNI (User Network Interface) or ENNI (External Network to Network Interface) by which the service is provided to the customer, and an EVC that establishes a communication relationship between one or more UNIs or ENNIs. In Metro Ethernet services, there are three types of EVC: point-to-point, multipoint-to-multipoint and point-to-multipoint.
Another type of service being deployed over Ethernet networks consists of transporting traffic at different network layers such as Layer 2 (Ethernet frames) and Layer 3 (IP packets).
A key component of the Ethernet test and turn-up functions and performance monitoring capabilities is latching loopbacks. A latching loopback (LLB) is a function within a device in an Ethernet network where Ethernet frames, IP Packets and/or higher layer data are returned to the entity which sent them. It is advantageous to have latching loopbacks available at as many different points in the network as possible for testing purposes; however the latching loopbacks should not, or should minimally, interfere with regular operation of the network, its device and network traffic.
Various different LLB protocols have been, and are being defined, such as those by the MEF. Traditionally, LLB functionality was intended to be implemented by various carrier Ethernet equipment such as Network Interface Devices (NIDs), bridges, switches, and testing equipment.
Latching loopback functions are not always supported on all networking equipment; and when supported, they may not be implemented consistently across different equipment vendors. This makes it difficult to manage the Ethernet network with a single network management system. It would be advantageous to be able to manage all or a majority of a network and its many different NEs with a single network management system.
When latching loopback functions are not implemented inside existing networking equipment, external Network Interface Devices (NIDs) boxes can be inserted in-between NEs to enable latching loopback functions. NIDs have some disadvantages because they introduce extra equipment into the network requiring extra rack space, extra power, extra cost and the additional NIDs may also cause additional networking issues.
FIG. 1 illustrates how latching loopback functions may be implemented in prior art networks. In FIG. 1, heterogeneous NEs 2, 4, 6, 8 are connected in a network 100 such as by fiber optical cabling. The NEs 2, 4, 6, 8 have ports to receive transceivers 12 which provide electro-optical interfaces between NEs 2, 4, 6, 8 over the network 100. Some NEs are provided by some manufacturers, some by others. Some NEs have latching loopback capability 14 while some do not. Network Element NE_A 2 implements latching loopback functionality 14 internally; however a wide variety of LLB implementations across different NEs makes managing all the different LLB interfaces in the network 100 difficult.
None of network elements NE_B 4, NE_C 6 or NE_D 8 implement latching loopback functions internally. Accordingly, to implement latching loopback functions between these LLB-deficient NEs, additional devices, in the form of NIDs 16, 18 may be installed, where possible, into the network between network elements 2, 4, 6, 8 on each path.
In the example in FIG. 1, installing NIDs 16, 18 is possible between NE_B 4 and NE_C 6 because, for example, the network administrator has access to the cabling between those two NEs and can physically interrupt those lines, install and manage additional NIDs. However, in FIG. 1, there are no NIDs between NE_C 6 and NE_D 8 because, for example, NE_D 8 may be located in a constrained location 20 where no NIDs could be added. In many cases, certain parts of the Ethernet network 100 cannot be covered, or would be excessively difficult to cover with LLB by the addition of NIDs due to physical constraints, such as NEs that are poles. As a result, it is common for LLB to be unavailable in parts of the network 100. Although NE_A 2 and the NIDs 16, 18 implement LLB 14, it is common that they do not share the same management interface making managing all of the LLBs difficult and disconnected. It would be advantageous to have a simple, cost effective and unified way to add Layer 2, Layer 3 and higher layer latching loopback functionality on existing network equipments.